I agree with gray raven: I want to know where (and, if possible, when) as well as who. If you just say "Shakespeare," and I don't recognize the quote, it could be from a sonnet, and therefore possibly Shakey's own feelings on the subject, or it could be Hamlet, Shylock, or Caliban's thoughts we're getting. Makes a difference to me. The Web is packed with whole lists of quotations each attributed only to a person, and sometimes the wrong person, and these lists get copied and re-posted until it's impossible to find the right source. At least if it were common practice to cite the work or the occasion it might minimize the damage. And I wouldn't have to read all of Shakespeare just to find the context.